As an example of local drug delivery therapy, there has been a drug-eluting stent (DES). The DES is so designed as to locally release a drug in a sustained manner for a long period of time, thereby preventing restenosis of a blood vessel. The sustained release of a drug from the DES is achieved by a polymer conjugate such as polylactic acid (PLA). In this case, since the polymer remains in a living body for a long period of time, there is a problem of severe complications such as chronic inflammation or delayed thrombosis at the affected part of a lesion.
Conventionally, it has been reported that sustained release of a drug for a long period of time is necessary for restraining restenosis. In recent years, however, it has been being made clear that by rapid transfer of a drug to a target tissue, even a short-term sustained drug effect is sufficient for successfully preventing restenosis. The technology of rapid drug delivery does not need a polymer matrix, such as PLA (polylactic acid) or PLGA (polylactic acid-glycolic acid copolymer), for sustained release, and is therefore advantageous for avoiding complications.
Besides, in recent years, development of DEBs (Drug Eluting Balloons) wherein a balloon catheter is coated with a drug has been made positively, and it has been reported to be effective in treating and preventing restenosis. The balloon is coated with a coating that contains a drug and additives, and, when a blood vessel is dilated, the balloon is pressed against the blood vessel wall so as to deliver the drug to the target tissue.